(1) FIELD OF THE INVENTION
This invention relates to grass mowers.
(2) PRIOR ART
Grass mowers of the rotary type are well known. These comprise a mower body carrying a motor which drives a horizontal rotary disc to which the grass cutter blades are attached. Such mowers are often provided with a grass catcher in which case the cutter blades may be shaped so as to create an air stream by means of which the grass clippings are conveyed to the catcher. This conveyance may be via an annular chute formed in the mower body and extending above and around the path of movement of the cutter blades. The chute commonly has a generally helical roof so that the height of the chute increases from a lowermost point at one end thereof to a highest position at a delivery end of the chute which in use communicates via an opening in the mower body with the grass catcher.
Generally speaking, to obtain satisfactory performance from mowers of the above kind, it is necessary to operate the mower so that the cutter blades are rotated at a relatively high speed in order that a sufficient air flow will be provided in order to adequately deliver grass cuttings into the chute for delivery to the grass catcher. Because of this, the selected operating speed is usually greater than is necesary or even desirable for effective grass cutting. One effect of this is that grass cutting and collecting under certain conditions, such as where the grass is wet, may be less efficient than is desirable and also results in the mower being noisier to operate than would otherwise be the case. In particular, with regard to the latter, many mowers of the kind in question are operated by small internal combustion engines which are particularly noisy when operated at speeds necessary to ensure effective grass catching.
The specification of U.S. Pat. No. 2,953,888 (J. T. Philips Jnr. et al) describes a rotary type harvester having a body which encompasses a disc thereunder, the disc being rotatable about an upright axis and having cutter blades thereon for effecting harvesting of green forage over which the harvester is in use moved. This harvester includes fan blades on the top of the disc and these blades, in use of the harvester generate an air flow which is used to entrain, elevate and convey the severed crop material within a downwardly open space of the body within which the disc is housed. Severed crop material is by this means conveyed away from the harvester via a discharge opening which communicates with a tangentially arranged discharge tube comunicating with the said space. Deflection of severed material into this discharge tube is arranged by means of an upright baffle depending from the roof of space within which the mower disc and cutter blades are housed and extending outwardly from the disc axis over the cutter blades and also outboard of the cutter blades. In use of the harvester, air is admitted into the interior space in the harvester body and the fan blades operate to direct cuttings against the interior baffle plate for deflection into the discharge tube.
Whilst this mower utilizes fan blades to effect transport of grass cuttings, the transport is effected by an air flow which is outward and somewhat downward and is directed to cooperate with the fixed baffle plate for deflection of the grass cuttings to the discharge pipe. The arrangement is not directed to utilization of fan generated air flow in mowers of the kind having an annular conveying chute.